Buckinghamshire CC ANPR cameras

[Roland Perry]

In article 
<CAJkBBXUqnXa9LGxMtHcesRS-nybarEEBtBeb34U5OCA8vk5Uxw at mail.gmail.com>, 
John Wilson <tugwilson at gmail.com> writes
>>> Obviously  there's detail to work through such as: a vehicle enters the
>>> area, is  seen by ANPR on entry, then parks up for several days and isn't
>>> seen  by a second ANPR camera; at what point do you delete the partial
>>>  journey record that will, of necessity, still contain a registration
>>>  number.
>>
>> About an hour after last seeing the plate would be plenty if you are looking
>> at the "flow" of traffic.
>
>That's quite true but it seems clear from the Council documents that
>they intend to hold the camera even data for some time. There are
>perfectly legitimate reasons for this. They can, no doubt, get useful
>information from the bulk data which would help in planning traffic
>management.

Unless the entire perimeter is covered (cf London Congestion Charge) 
then vehicles that 'disappear' could just as easily have taken an 
unmonitored exit. Indeed, schemes like the London CC only logs entries, 
and not exits, I thought.
-- 
Roland Perry